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Old 03-05-2011, 12:02 PM   #1
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Heat coils on same time w/ AC


I have a Carrier HP that is ~ 12yrs old. About 2 weeks ago I woke up to a bad smell in the house and cold temps. Quickly realized that even though the heat was on, the fan was not turning on. Opened the unit, and the blower motor was super hot. Replaced motor which had seized up. I also found that the white control wire was broken at the outside unit and not making a connection at all. I just happened to notice that; wasn't looking at those wires specifically. I re-made the connection. Turned on power, and I see that the auxiliary heater coils turned on....even though the thermostat was set on AC! The AC had not turned on yet, b/c i had not lowered the temp on the thermostat. Shut system down, remove heater coil kit KFQEH0601F20 and clean all dust, check fuses and connections. Notice that one of the heat sequencers is loose. When I slightly pull, it separates in 2 so the bottom half is still riveted tightly to the plate and top half is connected to wires and hanging loosely. The dielectric metal switch plate from inside the HS is accessible now. I reconnect everything and try to snap the HS together although I never hear it click or feel totally seated. Turn on power to the unit, and again, right away the heater coils turn on even though the unit is set on 'cool'.
Even if the HS was bad, the heat coils should not turn on; especially when the unit is set on 'cool' at the thermostat. Also note, the fan did not turn on when the heater coils turned on. I thought there was a safety circuit built into the system to prohibit this.
So, when I turn on the AC, the heater coils are also running during the cooling process. I think that during the time that the AC cycles off, the heater coils turn on. When the AC turns back on, the initial air from the vent is warm and has the smell of the heat coils. After a few seconds, the air blows cool. I don't know if the heater coils are on during the time the AC is on or through the whole cycle, or just when the AC is off. My work around at this point, in order to have AC, is to disconnect power to the heater coils.

I am confused....
1. Is the heat sequencer supposed to open in sections as i describe above?
2. Is the problem with the control board with a relay that is stuck?
3. If it is the control board, could that be why the fan is not turning on when the heat coils turn on?

HELP... I've enjoyed reading the other posts and see there are some top notch techs/engineers that would recognize my issue and have the answers. Thanks in advance!

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Old 03-05-2011, 12:30 PM   #2
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Heat coils on same time w/ AC


Check your thermostat. Disconnect all thermostat wires. After that make connection between the wires R (24v), Y(Cool) and G (Fan). You should have only your AC working. Let's us know what happen after that.

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Old 03-05-2011, 12:45 PM   #3
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Heat coils on same time w/ AC


I have to run out for commitments for the rest of the day. I probably won't post again until tomorrow morning....thanks for the quick response!
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Old 03-05-2011, 07:54 PM   #4
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Heat coils on same time w/ AC


The heat sequencer will need replacing. This may solve your entire problem. Certainly the fact that it's in pieces is a problem in itself.

Another posibility: the white wire outside may have been disconnected for a reason. This is all speculation based on the limited info you provide, but it may well be that the defrost control in the outdoor heat pump is stuck closed, forcing the elements to run. Try disconnecting the white wire and see if the elements still come on.

And again, have that heat sequencer replaced.

Last edited by rightit; 03-05-2011 at 08:01 PM.
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Old 03-06-2011, 05:00 AM   #5
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Heat coils on same time w/ AC


Probably just need to replace that bad sequencer. broken like that it will keep turning on your heat no matter what your thermostat is set to.
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Old 03-09-2011, 05:01 PM   #6
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Heat coils on same time w/ AC


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Originally Posted by JJboy View Post
Check your thermostat. Disconnect all thermostat wires. After that make connection between the wires R (24v), Y(Cool) and G (Fan). You should have only your AC working. Let's us know what happen after that.
JJBoy,

I disconnected all of the wires from the thermostat, energized the unit, ONLY connected the fan (G) and 24v(R) and the fan relay kicked in and the fan started. I immediately unconnected the wires and the fan continued to run for ~1 minute. While running I went in the attic to the unit where I had already removed the covers. Fan is running, I can't see the glow from the heater coils, however, I the unit casing just above the heater coils IS warm to the touch whereas directly over the fan it is NOT. The fan shuts off and again, I cannot see any glow from the heater coil. Since I could feel the heat I disconnected one of the two electrical disconnects that supply power to the heater coils. I go downstairs and I can smell the same smell, like the heater was running.
Next, after waiting about 5 minutes for the unit to cool down, with nothing running I go back into the attic and energize the disconnect to the heater. Immediately I can see the glow from the heater coils. I pulled the disconnect again and this is where I stand.

Does this mean that it is the heat sequencer as indicated by others? I thought the heat sequencer was only used to time the turning on of the coils in stages; not to energize the heating unit.

Thoughts?
I let the unit sit for 5 mins and confirm
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Old 03-09-2011, 05:16 PM   #7
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Heat coils on same time w/ AC


The sequencer does provide timing for your heaters to come on, but is also the switching mechanism by which the elements are energized. If you follow the wires from the sequencer you will see that the bottom set of contacts are powered from the control system and the top contacts allow power from the unit to go to the elements on one side and the other side of the element goes through a limit control and back to the other side of your power supply. Sequencer is most likely candidate for trouble, especially if it came apart as stated, contacts will be welded and element will never shut off whenever power is applied to unit no matter if it is in heating or cooling. If you have a volt meter you can check and see if you have 24 volts at the bottom conection to the sequencer, if you do then the control circuit is asking for the elements to be energized, if not then your sequencer is stuck. I think you already proved this though when you unhooked the stat and the elements came on.
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Old 03-09-2011, 05:33 PM   #8
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Heat coils on same time w/ AC


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Originally Posted by HVACDave View Post
The sequencer does provide timing for your heaters to come on, but is also the switching mechanism by which the elements are energized. If you follow the wires from the sequencer you will see that the bottom set of contacts are powered from the control system and the top contacts allow power from the unit to go to the elements on one side and the other side of the element goes through a limit control and back to the other side of your power supply. Sequencer is most likely candidate for trouble, especially if it came apart as stated, contacts will be welded and element will never shut off whenever power is applied to unit no matter if it is in heating or cooling. If you have a volt meter you can check and see if you have 24 volts at the bottom conection to the sequencer, if you do then the control circuit is asking for the elements to be energized, if not then your sequencer is stuck. I think you already proved this though when you unhooked the stat and the elements came on.
HVACDave,

Thanks for the insight into the purpose of the sequencer. So, my next step is to replace the sequencer. From what I can see, they are riveted onto the steel plate that mounts onto the heater unit. I have seen on the web where I can buy the individual sequencer, but where can I buy the plate that contains both of them?

Thanks for the assistance!
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Old 03-09-2011, 05:43 PM   #9
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Heat coils on same time w/ AC


Your local contractor supply will stock, you may even be able to buy at home depot (not sure). They sell them in singles or doubles and either/or are riveted to the metal plate, but usually there is one screw that holds the whole metal plate onto the unit and you replace the whole assembly.
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Old 03-09-2011, 05:58 PM   #10
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Heat coils on same time w/ AC


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Originally Posted by HVACDave View Post
Your local contractor supply will stock, you may even be able to buy at home depot (not sure). They sell them in singles or doubles and either/or are riveted to the metal plate, but usually there is one screw that holds the whole metal plate onto the unit and you replace the whole assembly.
I think this is the assembly that I need to order. I am going to pull mine out tonight to get the numbers off, and confirm before ordering. Once I get it in and reassemble and test, I'll post a follow up.

Thanks everyone for the quality responses!

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Last edited by reevtd; 03-09-2011 at 05:58 PM. Reason: i forgot to add the link ... http://www.hvacpartsoutlet.com/Carrier-Bryant-Sequencer-HN67QG005.aspx
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